Polyester block compatibilizer for polyethylene polypropylene blends

ABSTRACT

The present invention relates to a composition comprising polypropylene, polyethylene and a compatibiliser, wherein said compatibiliser is a block copolymer comprising a polypropylene block and a polyester block, said polyester being a non-aromatic polyester and having an average M/E ratio of at least 10, wherein M is the number of backbone carbon atoms in the polyester not including the carbonyl carbons and E is the number of ester groups in the polyester.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a 371 of International Application No. PCT/EP2016/061114, filed May 18, 2016, which is incorporated herein by reference in its entirety, and which claims priority to European Application No. 15169057.5, filed May 22, 2015.

The present invention relates to a composition comprising polypropylene, polyethylene and a compatibiliser.

Compositions of polypropylene and polyethylene are desirable as they potentially allow tuning of the material properties by selecting the type and amounts of the individual components. However, it is well known that polyethylene and polypropylene are immiscible. It is further a disadvantage that polypropylene and polyethylene substantially do not interact so that a blend of polyethylene and polypropylene generally results in a two phase system having a polypropylene phase and a polyethylene phase with poor physical properties. Further, polyolefins generally require pretreatment such as corona, flame or fluorine treatment before they can be printed.

Accordingly attempts have been made to increase the interaction between the phases in such blends by adding a compatibiliser. Compatibilisers are materials that have affinity with both phases and enhance the bonding strength. As a result a material with improved properties can be obtained.

Blends of polypropylene and polyethylene comprising a compatibiliser are known in the art. For example U.S. Pat. No. 6,114,443 discloses a composition comprising a blend of polyethylene and an isotactic poly-alpha-olefin homopolymer (such as polypropylene), together with a diblock copolymer compatibiliser of polyethylene block and an atactic poly-alpha-olefin block. The diblock compatibiliser of this US patent may be prepared using sequential polymerisation of the monomers for each block in the presence of a metallocene catalyst.

In view of the advantageous combination of mechanical properties, chemical properties and cost there is a continuous need for further compositions that can be manufactured relatively easy and with low cost.

It is therefore an object of the present invention to provide for a composition comprising polypropylene and polyethylene, which composition has a good balance of mechanical properties.

It is a further object of the present invention to provide a polyolefin based composition with improved printability.

Accordingly the present invention relates to a composition comprising polypropylene, polyethylene and a compatibiliser, wherein said compatibiliser is a block copolymer comprising a polypropylene block and a polyester block, said polyester being a non-aromatic polyester and having an average M/E ratio of at least 10, wherein M is the number of backbone carbon atoms in the polyester not including the carbonyl carbons and E is the number of ester groups in the polyester.

The present inventors have found that non-aromatic polyesters having an average M/E ratio of at least 10, wherein M is the number of backbone carbon atoms in the polyester not including the carbonyl carbons and E is the number of ester groups in the polyester, may, at least in part, co-crystallise with polyethylene crystals, and/or may crystallise epitaxially onto polyethylene crystals. The present inventors also observed that the polypropylene block shows interaction with the polypropylene. Accordingly, the present inventors found that a block copolymer as herein acts as a compatibiliser in a blend of polypropylene and polyethylene and further observed that the properties of the polyethylene-polypropylene blend are improved by addition of a relatively small amount of the compatibiliser as herein defined. Further, since the polyester compatibiliser will introduce a certain polarity in the material the printability is improved such that pre-treatment prior to printing can be avoided or is at least reduced in intensity.

By application of the invention at least some of the aforementioned objects are met.

The FIGURE is a graphical representation of a DSC analysis graphed as temperature versus heat flow.

Compatibiliser

Polyester Block

The polyester block in the compatibiliser of the composition according to the present invention is a non-aromatic polyester having an average M/E ratio of at least 10, wherein M is the number of backbone carbon atoms in the polyester not including the carbonyl carbons and E is the number of ester groups in the polyester. With average M/E ratio is meant a numerical average. The M/E ratio may also be at least 12, at least 20, at least 50 or even at least 100. It is however advantageous for printability to find a balance between on the one hand the interaction with the polyethylene phase and sufficient introduced polarity into the material. Accordingly it is preferred that the M/E ratio is at most 50, preferably at most 32. Hence a preferred range for the M/E ratio in the polyester block is from 10-32.

The polyester is non-aromatic meaning the polyester does not contain aromatic groups.

The backbone of the polyester is preferably saturated meaning it preferably does not contain any double bonds. It is preferred the backbone of the polyester is aliphatic. The polyester backbone may, in an embodiment, contain short aliphatic branches such as methyl, ethyl, propyl, butyl, pentyl or hexyl branches. The amount of such branches is preferably kept at a low amount since it may negatively affect the (co)crystallisation behaviour of the polyester block. In another embodiment the backbone contains one or more heteroatoms such as oxygen, nitrogen or sulfur.

The polyester may be a polyester homopolymer or a polyester copolymer.

If the polyester is a polyester copolymer then the number of backbone carbon atoms between two neighboring ester groups in the backbone is preferably randomly distributed over the polyester. Furthermore the number of backbone carbon atoms (M) between ester functionalities in polyester copolymers is preferably at least 8, more preferably at least 10, or at least 12.

Typical examples of polyester homopolymers include the hompolymers obtainable by the ring opening polymerisation of dodecalactone, tridecanolactone, tetradecalactone, pentadecalactone, hexadecalactone, heptadecalactone, octadecalactone, nonadecalactone, ambrettolide, globalide. In other words typical examples of polyester homopolymers include polydodecalactone, polytridecanolactone, polytetradecalactone, polypentadecalactone, polyhexadecalactone, polyheptadecalactone, polyoctadecalactone, polynonadecalactone, polyambrettolide, polyglobalide.

Typical examples of polyester copolymers include copolymers of at least two lactones from a group including dodecalactone, tridecanolactone, tetradecalactone, pentadecalactone, hexadecalactone, heptadecalactone, octadecalactone, nonadecalactone, ambrettolide, globalide, valerolactone, caprolactone, massoia lactone, δ-decalactone, ε-decalactone, 13-hexyloxacyclotridec10-en-2-one, 13-hexyloxacyclotridecan-2-one.

Other typical examples of polyester copolymers include AABB type copolyesters prepared of a combination of C₂-C₃₀ diols and C₂-C₃₂ diacids provided the polyester copolymer has an average M/E of at least 10. Further it is preferred that the M/E ratio for the copolymers is at least 8. The term C_(x) refers to the amount of carbon atoms x in the diol or diacid respectively.

Diols include, but are not limited to, ethylene glycol, propane-1,3-diol, butane-1,4-diol, pentane-1,5-diol, hexane-1,6-diol, heptane-1,7-diol, octane-1,8-diol, nonane-1,9-diol, decane-1,10-diol, undecane-1,11-diol, dodecane-1,12-diol, tridecane-1,13-diol, tetradecane-1,14-diol, pentadecane-1,15-diol, hexadecane-1,16-diol, heptadecane-1,17-diol, octadecane-1,18-diol, nonadecane-1,19-diol, icosane-1,20-diol, henicosane-1,21-diol, docosane-1,22-diol, tricosane-1,23-diol, tetracosane-1,24-diol, pentacosane-1,25-diol, hexacosane-1,26-diol, heptacosane-1,27-diol, octacosane-1,28-diol, nonacosane-1,29-diol, triacontane-1,30-diol as well as their unsaturated and branched analogues. The lactone might also contain a hetero atom in the main chain like an oxygen, nitrogen or sulfur—for example 1,5-dioxapan-2-one.

Cyclic carbonic acid esters can also be used as monomer or as comonomer in combination with lactones, dilactones, hydroxyl acids, hydroxyacid esters or diols plus dicarboxylic acids or a combination of these monomers to form polycarbonates or poly(ester-co-carbonate)s with an average M/E of 10 or larger. Examples of cyclic carbonic acid esters are trimethylene carbonate and decamethylene carbonate.

Diacids include, but are not limited to oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, heptanedioic acid, octanedioic acid, nonanedioic acid, decanedioic acid, undecandedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, heptadecanedioic acid, octadecanedioic acid, nonadecanedioic acid, icosanedioic acid, henicosanedioic acid, docosanedioic acid, trocosanedioic acid, tetracosanedioic acid, pentacosanedioic acid, hexacosanedioic acid, heptacosanedioic acid, octacosanedioic acid, nonacosanedioic acid, triacontanedioic acid and their unsaturated and branched analogues. The diols and diacids might also contain a heteroatom in the main chain like an oxygen, nitrogen or sulfur.

Instead of a combination of one or more diol and diacid, cyclic dilactones can also be added to produce AABB copolyesters with the desired M/E, which is 10 or higher. Typical examples of cyclic dilactones are: ethylene adipate, ethylene brassylate, butylene adipate.

Another type of polyester copolymers include AB/AABB copolyesters prepared of a combination of lactones and dilactones and/or the combination of C₂-C₃₀ diols and C₂-C₃₂ diacids, which result in polyesters having an average M/E of at least 10. The lactones, dilactones, diols and diacids can be selected from the lists given above.

Preferably the polyester or copolyester is selected from polytetradecalactone, polypentadecalactone, polyhexadecalactone, poly(caprolactone-co-pentadecalactone), poly(ε-decalactone-co-pentadecalactone), poly(ethylene brassylate-co-pentadecalactone), poly[ethylene-1,19-nonadecanedioate], poly[ethylene-1,23-tricosanedioate], poly[propylene-1,19-nonadecanedioate], poly[propylene-1,23-tricosanedioate], poly[1,4-butadiyl-1,19-nonadecanedioate], poly[1,4-butadiyl-1,23-tricosanedioate], poly[1,6-hexadiyl-1,19-nonadecanedioate], poly[1,6-hexadiyl-1,23-tricosanedioate], poly[1,19-nonadecadiyl-1,19-nonadecanedioate], poly[1,19-nonadecadiyl-1,23-tricosanedioate], poly[1,23-tricosadiyl-1,19-nonadecanedioate], poly[1,23-tricosadiyl-1,23-tricosanedioate], poly[1,20-icosadiyl-1,20-icosa-nedioate], poly[1,6-hexadiyl-1,20-icosanedionate], poly[propylene-1,20-icosanedionate].

More in general the polyester or copolyester is of general structure

wherein

R^(x) is an organic group, preferably an aliphatic group having an average chain length of at least 10 carbon atoms and n₁ is the number of repeating units, which generally is at least 25, preferably at least 50 such as at least 100. The number of repeating units n1 is preferably at most 2000, such as at most 1000 or 500.

Organic group R^(x) is a branched or straight hydrocarbon group optionally containing one or more heteroatoms provided that the atom neighboring the —O— is a carbon atom, i.e. not a heteroatom. R^(x) may contain one or more unsaturations, like —C═C—. Preferably R^(x) is a branched or straight hydrocarbon group, more preferably R^(x) is a branched or straight aliphatic group. R^(x) is preferably a saturated aliphatic group. In that respect the term chain length as used herein refers to the shortest number of atoms between two ester functionalities (O═)C—O—. Hence the “chain length” does not include any optional branches or side groups. For example, if R^(x) is (C₄H₈) the chain length is four. Similarly, if R^(x) is CH₂—C(CH₃)₂—CH₂—CH₂ the chain length is also four. In the general formula above Rx may be the same or different throughout the polyester provided the average chain length is at least 10 carbon atoms. The following general (co)polyester structures can be considered, which structures are more detailed embodiments of the general structure provided above:

The chain lengths of R¹, R², R³ and R⁴ are selected such that for the polyester the M/E ratio is at least 10. The description for R^(x) above also applies for R¹-R⁴.

The average M/E ratio is preferably at least 12. The higher the M/E ratio is the more the polyester will resemble polyethylene and the better the interaction with the polyethylene phase will be. At the same time, the manufacture of polyesters with very high M/E ratio is less cost-effective. In addition the polarity of material will then be lower so that printability requires pre-treatment.

Accordingly the M/E ratio may be at most 32. Hence the M/E ratio is may be from 10-32, more preferably from 12-24.

Polypropylene Block

The polypropylene block in the compatibiliser of the composition according to the present invention is a propylene homopolymer or a propylene copolymer containing at least 90 wt. % of propylene on the basis of the weight of the polypropylene block. Comonomers may be ethylene or C3-C8 α-olefins, preferably ethylene. Preferably the amount of comonomer is at most 5 wt. %, more preferably at most 2 wt. %. If the amount of comonomer is too high the material may become fully amorphous which from a viewpoint of mechanical properties is not desirable in certain applications.

Type of Block Copolymer

The block copolymer according to the present invention is preferably of the type AB or BAB with A representing polypropylene and B representing polyester.

The block copolymer may also be a graft block copolymer of structure AB_(n) having a polypropylene backbone with n polyester branches grafted thereon, n being at least 1. For graft copolymers the backbone is considered as the polypropylene block.

The amount of grafts n is at most 20, preferably at most 15 or 10. The number of grafts not be too high because otherwise the polypropylene backbone will not interact sufficiently with the polypropylene phase in the composition.

In an embodiment where a block copolymer contains two or more B (i.e. polyester) blocks these B blocks may be the same or different in length, i.e. may have the same or different molecular weight, depending on the conditions of the process to manufacture the block copolymer.

The number average molecular weight of the block copolymer used in the composition as compatibiliser is preferably from 5000 to 250000 g/mol, more preferably from 10000 to 100000 g/mol, said number average molecular weight being determined as the polyethylene-equivalent molecular weight by high temperature size exclusion chromatography performed at 160° C. in trichlorobenzene using polyethylene as standard.

Method of Manufacture: Block Copolymer

In an embodiment the block copolymers can be manufactured by a three-step method.

In a first step (A) propylene and optionally an olefinic comonomer is/are polymerised using a catalyst system to obtain a first polypropylene block containing a main group metal on at least one chain end; the catalyst system comprising:

i) a metal catalyst or metal catalyst precursor comprising a metal from Group 3-10 of the IUPAC Periodic Table of elements; and

ii) at least one type of chain transfer agent; and

iii) optionally a co-catalyst;

Thus, in step (A) a polypropylene or poly(propylene-co-α-olefin) is being prepared by means of coordinative chain transfer polymerization (CCTP) in the presence of a catalyst, cocatalyst, at least one type of chain transfer agent and optionally an additional chain shuttling agent. Chain transfer agents used are typically aluminum-, boron- and/or zinc hydrocarbyl species). This process results in polypropylene or poly(propylene-co-α-olefin) chains that are end-functionalized with a metal atom, which is susceptible to react with an oxidizing agent such as oxygen.

In a second step (B) the first polypropylene block containing a main group metal on at least one chain end obtained in step A) is reacted with at least one type of oxidizing agent and subsequently at least one type of metal substituting agent to obtain a first polypropylene block containing at least one functionalised chain end. Preferably the functionalised chain end comprises a hydroxyl group.

Thus, during step (B), the product obtained from step (A) is treated with oxygen followed a protic substrate, such as acidified alcohol, to remove the metal, to afford a hydroxyl end-functionalized polypropylene or poly(propylene-co-α-olefin) product.

In a third step (C) at least one second polymer block is formed on the first polypropylene block, wherein as an initiator the functionalized chain end of the first polypropylene block obtained in step B) is used to obtain the block copolymer. The third step can be performed by transesterification or ring opening polymerisation (ROP) of (suitable) lactones.

Thus, in step (C) the product of step (B) is used as a macroinitiator for the formation of the diblock copolymer. During step (C), a ring-opening polymerization of lactones or a transesterification of a pre-synthesized polyester is carried out in the presence of the hydroxyl chain-end functionalized polypropylene or poly(propylene-co-α-olefin) product during step (B) and a ring-opening polymerization and/or transesterification catalyst. Step (C) can be carried out in a (aromatic) hydrocarbon solution or in the melt. The process for the production of polypropylene or poly(propylene-co-α-olefin)-polyester block copolymers, is similar as has been reported for e.g. HDPE-PLLA di block copolymers (Chem. Eur. J. 2012, 18, 13974-13978) or for syndiotactic PP-polyester diblock copolymers (Macromolecules 2010, 42, 3073-3085). The transesterification reaction is comparable as reported for the coupling of poly(ethylene-co-vinyl alcohol) and polycaprolactone (Macromol. Mater. Eng. 2009, 294, 643-650).

The steps A to C described above can thereby also be performed in cascade-like process for example either in the same or in subsequent/connected reactors or vessels, preferably without additional intermediary and/or workup and/or drying and/or purification steps, even more preferred continuously. In a cascade-like process, the polymer preparation can be carried out without a metal-substitution step, for example by hydrolysis. It should be noted that an extruder can also be considered as a reactor in the context of the present invention.

Method of Manufacture: Graft Block Copolymer

The graft block copolymer, i.e. the block copolymer wherein polyester blocks are grafted on or from a polypropylene backbone, can be manufactured by a three-step method.

In a first step (D) at least one first type of olefin monomer and at least one second type of metal-pacified functionalized olefin monomer are copolymerised using a catalyst system to obtain a polypropylene main chain having one or multiple metal-pacified functionalized short chain branches, the catalyst system comprising:

-   -   i) a metal catalyst or metal catalyst precursor comprising a         metal from Group 3-10 of the IUPAC Periodic Table of elements;     -   ii) optionally a co-catalyst;         Thus is step (D) propylene is being copolymerized using a         pacified hydroxyl functionalized olefin comonomer in the         presence of a catalyst and a cocatalyst, similarly as any other         catalytic olefin copolymerization, with the difference that the         hydroxyl-functionalised olefinic comonomer is pacified by         reacting it with an aluminum alkyl such as TiBA prior to the         copolymerization.

In a second step (E) the polypropylene main chain having one or multiple metal-pacified functionalized short chain branches obtained in step (D) is reacted with at least one metal substituting agent to obtain a polypropylene main chain having one or multiple functionalized short chain branches; Preferably the functionalised chain end comprises a hydroxyl group.

Thus, during step (E), the protective group is removed by treating the product of step (A) with a protic substrate such as acidified alcohol. The product of step (E) is a random copolymer of propylene and hydroxyl-functionalized olefins, where the hydroxyl functionalities are located in the short chain branches.

In a third step (F) one or more polyester side chains are formed on the polypropylene main chain, wherein as initiators the functionalized short chain branches on the polypropylene main chain obtained in step (E) can be used to obtain the graft copolymer. Step (F) can be performed by transesterification or by ring opening polymerisation (ROP) of (suitable) lactones.

Thus, the product of step (E) is subsequently used in step (F) as a macro-initiator for the formation of graft block copolymer. During step (F), a ring-opening polymerization of lactones or a transesterification of a pre-synthesized polyester is carried out in the presence of the random copolymer of propylene and hydroxyl-functionalized olefins obtained in step (B) and a ring-opening polymerization and/or transesterification catalyst.

Step (C) can be carried out in a (aromatic) hydrocarbon solution or in the melt. The process for the production of propylene and hydroxyl-functionalized olefins and polypropylene-graft-polyester block copolymers, is similar as has been reported for e.g. ethylene and hydroxyl-functionalized olefin copolymerization and subsequent graft copolymer formation (J. Polym. Sci. Part A Polym. Chem. 2014, 52, 2146-2154). The transesterification reaction is comparable as reported for the coupling of poly(ethylene-co-vinyl alcohol) and polycaprolactone (Macromol. Mater. Eng. 2009, 294, 643-650).

The steps D to F described above can be performed in cascade-like process for example either in the same or in subsequent/connected reactors or vessels, preferably without additional intermediary and/or workup and/or drying and/or purification steps, even more preferred continuously. In a cascade-like process, the polymer preparation can be carried out preferably without a metal-substitution step, for example by hydrolysis. It should be noted that an extruder can also be considered as a reactor in the context of the present invention.

Polypropylene

The polypropylene in the composition may be:

-   -   one or more of a propylene homopolymer,     -   one or more of a propylene—α-olefin random copolymer, preferably         a propylene ethylene or a propylene C₄-C₈ α-olefin random         copolymer,     -   one or more of a propylene—α-olefin block copolymer,     -   one or more of a heterophasic polypropylene copolymer comprising         a matrix phase and a disperse phase, the matrix phase consisting         of a propylene homopolymer and/or a propylene copolymer with up         to 3 wt. % of ethylene and/or at least one C₄-C₈ α-olefin, the         wt. % being based on the matrix phase, and the disperse phase         consisting of an ethylene—C₃-C₈ α-olefin copolymer,     -   a mixture of any of the foregoing polypropylenes.

Isotactic polypropylene is preferred.

If the polypropylene is a heterophasic copolymer it is preferred that the matrix phase is a propylene homopolymer of a propylene-ethylene copolymer with up to 3 wt. % of ethylene and further that the disperse phase is an ethylene propylene copolymer with from 20-80 wt % of propylene and 80-20 wt. % of ethylene, the wt. % based on the disperse phase.

The polypropylene is preferably a propylene homopolymer or a propylene ethylene or a propylene C₄-C₈ α-olefin random copolymer. The random copolymer contains at most 5 wt. %, on the basis of the copolymer, of said ethylene or α-olefin. The random copolymer is preferably a propylene-ethylene random copolymer.

Preferably the melt flow rate of the polypropylene is from 0.1-100 g/10 min as measured in accordance with ISO 1133 (2.16 kg, 230° C.). More preferably the melt flow rate is from 5.0 to 60 g/10 min.

Polyethylene

The polyethylene in the composition according to the present invention may be a very low density polyethylene (VLDPE), linear low density polyethylene (LLDPE), low density polyethylene (LDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE). The polyethylene may also be a mixture of at least two or at least two types of the foregoing polyethylenes. For example the polyethylene may be a mixture of LLDPE and LDPE or it may be a mixture of two different types of LDPE.

The terms VLDPE, LDPE, LLDPE, MDPE and HDPE are known in the art.

Very low density polyethylene (VLDPE) generally means polyethylene with a density of less than 915 kg/m³. Linear low density polyethylene and low density polyethylene means polyethylene with a density of from 915 to 935 kg/m³. High density polyethylene means polyethylene with a density of more than 935 kg/m³.

Preferably the melt flow rate of the polyethylene is from 0.1-100 g/10 min as measured in accordance with ISO 1133 (2.16 kg, 190° C.).

Composition

The amounts of polypropylene and polyethylene in the composition may vary within wide limits. The amount of polypropylene may vary from 5-95 wt. % on the basis of the total amount of polyethylene and polypropylene. Preferably the amount of polypropylene is from 20-90 wt. %, 40-90 wt. %, 50-90 wt. % on the basis of the total amount of polyethylene and polypropylene. Accordingly the amount of polyethylene may vary from 95-5 wt. % on the basis of the total amount of polyethylene and polypropylene. Preferably the amount of polyethylene is from 80-10 wt. %, 60-10 wt. %, 50-10 wt. % on the basis of the total amount of polyethylene and polypropylene. In an embodiment the amount of polypropylene is from 60-90 wt. % and the amount of polyethylene from 40-10 wt. % on the basis of the total amount of polyethylene and polypropylene.

The melt flow rates of the compatibiliser, polypropylene and polyethylene are selected such that homogeneous blends can be prepared using common melt blending techniques, such as extrusion or internal mixing. In this respect a homogeneous blend means a blend wherein the polyethylene and polypropylene concentrations are substantially constant throughout the material, even though the polyethylene may form a disperse phase in the polypropylene matrix or vice versa. The compatibiliser needs to have a melt flow such that during the melt processing of the composition the compatibiliser can migrate, at least in part, to the interface of the polyethylene and polypropylene phase.

A preferred method of manufacture of the composition comprises the steps of

-   -   Preparing a masterbatch by melt mixing the polymer that will         form the disperse phase in the composition and the         compatibiliser,     -   Melt mixing the masterbatch so obtained with the polymer that         will form the matrix phase in the composition.

In this method it is preferred that a major part, preferably substantially all, of the compatibiliser is contained in the masterbatch and that a minor part, preferably substantially none, of compatibiliser is added during the melt mixing so as to form the composition. That is, during the step of preparing the masterbatch from 80-100% of the total amount of compatibiliser is added to the masterbatch and 0-20% of the total amount of compatibiliser is added during the step of preparing the composition from the masterbatch and the polymer that will form the matrix phase in the composition.

This method has the advantage that the compatibiliser is more effective resulting in optimised properties of the composition.

Accordingly the melt flow rate of the compatibiliser is preferably similar to the melt flow rate of the polymer forming the disperse phase. For example the ratio of melt flow rate of the polymer forming the disperse phase and the compatibiliser may range from 0.01-100, preferably from 0.05-50, more preferably from 0.1-10 even more preferably from 0.5-5, when measured under similar conditions.

The amount of compatibiliser is from 0.1-10 wt. %, preferably from 0.5-10 wt. % such as from 2-10 wt. % or 3-8 wt. % on the basis of the sum of the amount of polypropylene and polyethylene.

In a preferred embodiment the invention relates to a composition comprising

70-90 wt. % of polypropylene based on the sum of the amounts of polyethylene and polypropylene,

10-30 wt. % polyethylene based on the sum of the amounts of polyethylene and polypropylene,

1-10 wt. % compatibiliser based on the sum of the amounts of polyethylene and polypropylene,

wherein the polypropylene has a melt flow rate of from 1-20 (ISO 1133, 2.16 kg, 230° C.) the polyethylene is a low density polyethylene and having a melt flow rate of from 1-20 (ISO 1133, 2.16 kg, 190° C.) and the compatibiliser has a M/E ratio of from 10-32 and having a number average molecular weight of from 10000-100000 g/mol.

The composition may further contain additives common in the art such as dyes, pigments, antioxidants, ultra-violet stabilisers, infrared absorbers, flame retardants, mould release agents and the like. Such additives are comprised in an amount of up to about 5 wt. % on the basis of the weight of the composition.

The composition may also further comprise reinforcing agents like talc, glass fibres, glass flakes, glass platelets, organic fibres, carbon fibres, cellulosic fibres and the like. Talc and or glass fibres being preferred. The amount of reinforcing agent is from 1-20 wt. % on the basis of the weight of the composition.

A skilled person will understand that the composition according to the invention is a thermoplastic composition.

Articles

The present invention further relates to articles comprising the composition as disclosed herein. The present invention further relates to articles manufactured from the composition as disclosed herein. Generally the composition is converted into an article using a moulding technique such as injection moulding, extrusion moulding, blow moulding and compression moulding. Accordingly the present invention also relates to an article obtained by moulding the composition according to the present invention. It is also possible to manufacture profiles or tubes by means of profile or tube extrusion.

In the article obtained by moulding or extrusion at least part of the polyester block(s) of the compatibiliser co-crystallised and/or epitaxially crystallised in the polyethylene phase and at least part of the polypropylene block(s) of the compatibiliser entangled and/or co-crystallised and/or epitaxially crystallised in the polypropylene phase.

Articles may be automotive interior articles, automotive exterior articles, household appliances, pipes, films, sheets, containers, water containers, infuse bags.

Use

In another aspect the present invention relates to the use of a block copolymer comprising a polypropylene block and a polyester block, said polyester being a non-aromatic polyester and having an M/E ratio of at least 10, wherein M is the number of backbone carbon atoms in the polyester not including the carbonyl carbons and E is the number of ester groups as a compatibiliser in a blend of polypropylene and polyethylene. The preferred embodiments as set out herein for the composition likewise apply to this use.

The invention will now be further explained on the basis of the following non-limiting examples.

Measurement Methods

Conversion of reactions was determined by NMR:

¹H NMR analysis (¹H-NMR) carried out at 80-110° C. using deuterated tetrachloroethene (TCE-d₂) as the solvent and recorded in 5 mm tubes on a Varian Mercury spectrometer operating at frequencies of 400 MHz. Chemical shifts in ppm versus tetramethylsilane were determined by reference to the residual solvent.

Mn, Mw and PDI:

Mn, Mw (in kg/mol) and PDI were determined by means of high temperature size exclusion chromatography (SEC) which was performed at 160° C. using a high speed GPC (Freeslate, Sunnyvale, USA). Detection: IR4 (PolymerChar, Valencia, Spain). Column set: three Polymer Laboratories 13 μm PLgel Olexis, 300×7.5 mm. 1,2,4-Trichlorobenzene (TCB) was used as eluent at a flow rate of 1 mL·min⁻¹. TCB was freshly distilled prior to use. The molecular weights and the corresponding PDI were calculated from HT SEC analysis with respect to narrow polyethylene standards (PSS, Mainz, Germany). Size exclusion chromatography (SEC) of block copolymers was performed at 160° C. on a Polymer Laboratories PLXT-20 Rapid GPC Polymer Analysis System (refractive index detector and viscosity detector) with 3 PLgel Olexis (300×7.5 mm, Polymer Laboratories) columns in series. 1,2,4-Trichlorobenzene was used as eluent at a flow rate of 1 mL·min⁻¹. The molecular weights were calculated with respect to polyethylene standards (Polymer Laboratories). A Polymer Laboratories PL XT-220 robotic sample handling system was used as autosampler. Polydispersity, PDI, corresponds to M_(w)/M_(n).

Melting (T_(m)) and crystallization (T_(c)) temperatures as well as enthalpies of the transitions were measured by differential scanning calorimetry (DSC) using a DSC Q100 from TA Instruments. The measurements were carried out at a heating and cooling rate of 10° C.·min⁻¹ from −60° C. to 210° C. The transitions were deduced from the second heating and cooling curves.

Preparation of Polypropylene Block Having a Hydroxyl-Functionalized Chain End

The polymerization was carried out in a stainless steel stirred reactor having a reaction volume of 300 mL. The reactor was kept at a constant temperature of 40° C. Toluene (70 mL) and methylalumoxane (MAO) solution (5 mL of 30% solution in toluene, Al/Zr≈1000) were added and stirred at 50 rpm for 30 min. Triisobutylaluminium (TIBA; 4 mL, 1.0 M solution in hexanes, Al/Zr≈200 equiv.) and di-ethylzinc (DEZ; 1.0 mL, 1.0 M solution in hexanes, Al/Zr≈50 equiv.) were added and stirred for 10 min. Then a toluene solution of the zirconocene catalyst precursor, rac-Me₂Si(2-Me-4-Ph-Ind)₂ZrCl₂, was added. The solution was saturated with a predefined pressure of olefin—either ethylene or propylene. In a glove box, the catalyst was dissolved in toluene (3 mL) and transferred into the reactor. The reactor was then pressurized to the desired pressure (2 bars) of olefin and the pressure was maintained for a predefined time (15 min, step A)). At the end of polymerization, the olefin feed was stopped and after releasing the residual olefin pressure, air was injected through a gas injection tube and the suspension was maintained under constant oxygen pressure of 3 bars at 60° C. for 2 h with rigorous stirring (600 rpm, step B). At the end of oxidation step, the polymer was quenched in acidified methanol (used as metal substituting agent, step B)) to obtain the hydroxyl-functionalized first polypropylene block (iPP) that is then filtered, washed with methanol and dried at 60° C. in vacuum overnight.

The examples below relate to step C) of the process as described herein, wherein a second polymer block is formed using a previously prepared first polypropylene block having a functionalized chain end, especially for example a hydroxyl functionalized chain end.

Preparation of Block Copolymers

EXAMPLE 1

Typical Procedure for Synthesis of iPP-Block-PPDL Copolymers Via cROP.

A glass crimp cap vial was charged with toluene (1.5 mL), PDL (1.08 g, 4.5 mmol), hydroxyl end-capped iPP (17.4 mg, 8.7 μmol) and catalyst 2 (3.05 mg, 8.7 μmol).

All manipulations were carried out in the glovebox. Then, the mixture was removed from the glovebox and stirred in an oil bath at 100° C. The progress of the reaction was followed by ¹H NMR spectroscopy by taking aliquots at set time intervals. The synthesized copolymer was cooled to room temperature and quenched using acidified methanol, isolated and dried in vacuum at room temperature for 18 h. Table 1, entries iPP-PPDL1-iPP-PPDL9 specify the reaction conditions, molecular weight (M_(n) and M_(w)), PDI and the PDL conversion.

EXAMPLE 2

The same procedure was used as for example 1, with this difference that 2 was premixed with the hydroxyl end-capped iPP for 24 h at 100° C. Table 1, entries iPP-PPDL10-iPP-PDL15 specify the reaction conditions, molecular weight (M_(n) and M_(w)), PDI and the PDL conversion.

EXAMPLE 3

The same procedure was used as for example 2, with this difference that 1 was premixed with the hydroxyl end-capped iPP for 24 h at 100° C. Table 1, entries iPP-PPDL16-iPP-PDL21 specify the reaction conditions, molecular weight (M_(n) and M_(w)), PDI and the PDL conversion.

EXAMPLE 4

Typical Procedure for Synthesis of PP-Block-PPDL Via Reactive Extrusion.

The extruder temperatures of chambers were set at 160° C., 180° C., 190° C. in the first, second and third zone, respectively. The extruder was fed with maleic anhydride functionalized iPP (Exxelor PO1020, 9 g, M_(n)=30.7 kg·mol⁻¹, PDI=3.4, 0.43 wt % of anhydride groups) and Irganox B225 (2500 ppm). Polymer was premixed for 5 minutes and subsequently the ethanolamine (0.072 g, 1.1 mmol) was added via syringe. The mixture was processed for 60 s and then the extruder chamber was evacuated. The OH-functionalized polypropylene (Exx-OH) was purified by dissolution in m-xylene at 120° C. and precipitation in a cold acetone. The product was dried in a vacuum oven for 24 h at 40° C.

The previously prepared OH-functionalized PP was utilized for the preparation of PP-block-PPDL copolymers. In this step the extruder was fed with OH-functionalized polypropylene (Exx-OH) (5.1 g, M_(n)=36.6 kg·mol⁻¹, PDI=3.4) and polypentadecalactone (PPDL) (3.9 g, M_(n)=115.1 kg·mol⁻¹, PDI=2.4) at 190° C. with a screw speed set at 100 rpm. The polymers were premixed for 5 minutes. Then the tin (II) octoate catalyst 3 (0.045 g, 0.1 mmol) was added and the mixture was mixed for 2 minutes. The copolymer was purified by dissolution in m-xylene at 120° C. and precipitation in a cold acetone. The copolymer was dried in a vacuum oven for 24 h at 40° C. Table 1, entries iPP-PPDL22-iPP-PPDL24 specify the reaction conditions, molecular weight (M_(n) and M_(w)), PDI and the PDL conversion.

EXAMPLE 5

Typical Procedure for Synthesis of iPP-Block-PPDL Copolymers Via Transesterification in the Solution.

The OH-functionalized polypropylene (Exx-OH) (6.66 g, M_(n)=36.6 kg·mol⁻¹, PDI=3.4) and PPDL (3.33 g, M_(n)=39.6 kg·mol⁻¹, D=2.4) were placed in a three-necked round bottom flask equipped with a nitrogen inlet, reflux condenser and dissolved in m-xylene at 120° C. The solution was stirred using a magnetic stirrer. Then the catalyst 3 (0.05 g, 0.12 mmol) was added and the mixture was stirred for 24 h. The solution was poured into a beaker with cold acetone and stirred using magnetic stirrer for one hour and subsequently filtered. The copolymer was dried in a vacuum oven for 48 h at room temperature. Table 1, entries iPP-PPDL25-iPP-PPDL26 specify the reaction conditions, molecular weight (M_(n) and M_(w)), PDI and the PDL conversion.

TABLE 1 Ring-opening polymerization of PDL initiated by hydroxyl- end capped iPP affording iPP-block-PPDL copolymers. time temperature M_(n) M_(w) conv. Entry Cat. PDL/cat/in [h] [° C.] [g/mol] [g/mol] PDI [%] iPP-PPDL1 2 250/1/1 2 100 57906 107022 1.9 49 iPP-PPDL2 2 250/1/1 5 100 35991 70338 2.0 77 iPP-PPDL3 2 500/1/1 2 100 8786 17591 2.0 18 iPP-PPDL4 2 500/1/1 5 100 63193 122632 1.9 68 iPP-PPDL5 2 250/1/1 24 100 60365 98079 1.6 95 iPP-PPDL6 2 500/1/1 24 100 82483 149488 1.8 90 iPP-PPDL7 2 1000/1/1  24 100 102906 187201 1.8 91 iPP-PPDL8 2   500/1/1.2 24 100 64643 124188 1.9 86 iPP-PPDL9 2  1000/1/1.2 24 100 2728 15206 5.6 10 iPP-PPDL10* 2 250/1/1 2 100 7301 23323 3.2 38 iPP-PPDL11* 2 500/1/1 2 100 4860 14339 3.0 39 iPP-PPDL12* 2 1000/1/1  2 100 5203 18039 3.5 22 iPP-PPDL13* 2 250/1/1 5 100 33659 64170 1.9 19 iPP-PPDL14* 2 500/1/1 5 100 38402 69637 1.8 61 iPP-PPDL15* 2 1000/1/1  5 100 54029 80752 1.8 64 iPP-PPDL16* 1 250/1/1 2 100 14321 25906 1.8 32 iPP-PPDL17* 1 500/1/1 2 100 17635 29213 1.7 28 iPP-PPDL18* 1 1000/1/1  2 100 traces of product iPP-PPDL19* 1 250/1/1 5 100 33801 65196 1.9 75 iPP-PPDL20* 1 500/1/1 5 100 27246 47404 1.7 38 iPP-PPDL21* 1 1000/1/1  5 100 traces of product Copolymers synthesized by transesterification/catalyst 3 contribution 0.5 wt % PP/PPDL time temperature M_(n) M_(w) Entry Cat. wt/wt [h] [° C.] [g/mol] [g/mol] Ð iPP-PPDL22^(a) 3 3/5 0.03(2 min) 190 35.4 168.2 4.8 iPP-PPDL23^(a) 3 4/3 0.03(2 min) 190 31.7 167.5 5.3 iPP-PPDL24^(b) 3  2/1.5 0.03(2 min) 190 30.5 207.3 6.8 iPP-PPDL25^(c) 3 2/1 24 120 25.0 120.9 4.8 iPP-PPDL26^(a) 3 2/1  5 120 29.9 219.7 7.4 For the reactions marked with * the catalyst was reacted with the initiator at 100° C. for 24 h. ^(a)= M_(n) of PPDL used in the transesterification process is 85.5 kg/mol, ^(b)= M_(n) of PPDL used in the transesterification process is 115.1 kg/mol, ^(c)= M_(n) of PPDL used in the transesterification process is 39.6 kg/mol,

EXAMPLE 6

Typical Procedure for the Preparation of the Uncompatibilized Blends.

Isotactic polypropylene (iPP) (PP575P, 8.0 g, M_(n)=42.9 kg·mol⁻¹, PDI=6.9, MFI=10.5 g/10 min (230° C., 2.16 kg)), low density polyethylene (LDPE) (2008TN00, 2.0 g, M_(n)=12.2 kg·mol⁻¹, PDI=5.8, MFI=7.5 g/10 min (190° C., 2.16 kg)) were fed into the extruder chamber. The mixture was processed for 3 minutes at 190° C. with a screw rotation rate of 100 rpm. Afterwards the mixture was evacuated directly to a mini-injection molding machine to prepare samples for mechanical properties and morphology analysis. Table 2 entries 1, 2, 4, 6, 8 specify the blends preparation conditions.

EXAMPLE 7

Typical Procedure for the Preparation of the Blends Compatibilized by PP-Block-PPDL.

Isotactic polypropylene (iPP) (PP575P, 8.0 g, M_(n)=42.9 kg·mol⁻¹, PDI=6.9, MFI=10.5 g/10 min (230° C., 2.16 kg)), low density polyethylene (LDPE) (2008TN00, 2.0 g, M_(n)=12.2 kg·mol⁻¹, PDI=5.8, MFI=7.5 g/10 min (190° C., 2.16 kg)) and the PP-block-PPDL (iPP-PPDL24, 0.5 g, M_(n)=30.5 kg mol⁻¹, PDI=6.8) were fed into the extruder chamber. The mixture was processed for 3 minutes at 190° C. with a screw rotation rate of 100 rpm. Afterwards the mixture was evacuated directly to a mini-injection molding machine to prepare samples for mechanical properties and morphology analysis. Table 2 entries 3, 5, 7 specify the blends preparation conditions.

TABLE 2 Composition of the uncompatibilized and compatibilized by PP-block-PPDL polymer blends. weight ratio [PP]/[LDPE]/[PP- Mixing time Entry Composition block-PPDL] [min] 1 PP/LDPE/PP-block-PPDL 100/—/— 3 2 PP/LDPE/PP-block-PPDL 80/20/— 3 3 PP/LDPE/PP-block-PPDL 80/20/5 3 4 PP/LDPE/PP-block-PPDL 50/50/— 3 5 PP/LDPE/PP-block-PPDL 50/50/5 3 6 PP/LDPE/PP-block-PPDL 20/80/— 3 7 PP/LDPE/PP-block-PPDL 20/80/5 3 8 PP/LDPE/PP-block-PPDL —/100/— 3 For the preparation of the blends PP-block-PPDL (entry iPP-PPDL24, Table 1) as the compatibilizer was used.

FIG. 1 shows the DSC plots for these blends. It can be observed that the heat of crystallisation (enthalpy values) for compatibilised blends is lower as compared to blends that are not compatibilised. This is true for both the polypropylene phase as well as the polyethylene phase. Based on these observations the present inventors believe that the block copolymer as disclosed herein indeed has a compatibilising effect on blends of polyethylene and polypropylene.

Examples for Graft Block Copolymers:

Preparation of Polypropylene (iPP) Main Chain Having Hydroxyl-Functionalized Short Side Chain Branches

The copolymerization of propylene/10-undecen-1-ol using C₂-symmetric silyl-bridged zirconocene catalyst rac-Me₂Si(2-Me-4-Ph-Ind)₂ZrCl₂)/MAO has been conducted to synthesize randomly functionalized isotactic polypropylenes. Polymerization reactions were carried out in stainless steel Büchi reactors. Prior to the polymerization, the reactor was dried in vacuo at 40° C. and flushed with dinitrogen. Toluene solvent (70 mL) was introduced followed by TIBA and the functional monomer under an inert atmosphere. The resulting solution was stirred for 15-20 min followed by the addition of a calculated amount of cocatalyst under dinitrogen atmosphere. The polymerization reaction was started by addition of the catalyst to reactor. The reactor was then pressurized to the desired pressure with propylene and the pressure was maintained for a predefined time (step D)). The propylene feed was stopped and the resulting mixture was quenched in acidified methanol (used as metal substituting agent, step E)), filtered and dried under reduced pressure at 60° C. for 24 h.

All examples below relate to step F) of the process as disclosed herein, wherein polymer branches were formed using a previously prepared polypropylene main chain having a hydroxyl-functionalized short side chain branches.

Typical procedure for synthesis of iPP-graft-PPDL copolymers: A glass crimp cap vial was charged with toluene (1.5 mL), PDL (1.1 g, 4.5 mmol), hydroxyl-functionalized iPP (4.9 mg, 8.7 μmol) and catalyst 3 (˜3.05 mg, 8.7 μmol). All manipulations were carried out in the glovebox. Then, the mixture was removed from the glovebox and stirred in an oil bath at 100° C. The progress of the reaction was followed by ¹H NMR spectroscopy by taking aliquots at set time intervals. The synthesized copolymer was cooled to room temperature and quenched using acidified methanol, isolated and dried in vacuum at room temperature for 18 h. Table 2, entry iPP-PPDL1-HDPE-PPDL3 specifies the reaction conditions, molecular weight (M_(n) and M_(w)), Ð and the PDL conversion for the present example with catalyst 3 below.

Furthermore, the same procedure as above was used only with this difference that catalyst 4 below was used instead of 1. Table 2, entry iPP-PPDL4 specifies the reaction conditions, molecular weight (M_(n) and M_(w)), Ð and the PDL conversion for the present example with catalyst 2 below.

TABLE 2 Ring-opening polymerization of PDL initiated by hydroxyl- functionalized iPP affording iPP-graft-PPDL copolymers. mon/cat./ time T M_(n) conv. entry cat. initiator [h] [° C.] [g/mol] Ð [%] iPP-PPDL1 3 250/1/1 24 100 42000 2.4 95 iPP-PPDL2 3 500/1/1 24 100 50800 2.2 94 iPP-PPDL3 3 1000/1/1  24 100 84800 1.9 40 iPP-PPDL4 4 100/1/1 24 100 64400 2.0 16 

The invention claimed is:
 1. A composition comprising polypropylene, polyethylene and a compatibiliser, wherein said compatibiliser is a block copolymer comprising a polypropylene block and a polyester block, said polyester being a non-aromatic polyester and having an average M/E ratio of at least 10, wherein M is the number of backbone carbon atoms in the polyester not including the carbonyl carbons and E is the number of ester groups in the polyester.
 2. The composition of claim 1 wherein the compatibiliser is an AB or BAB type block copolymer with A representing polypropylene and B representing polyester, or a graft block copolymer of structure AB_(n) having a polypropylene backbone with n polyester branches grafted thereon, n being at least
 1. 3. The composition of claim 1 wherein the number of backbone carbon atoms between two neighboring ester groups in the backbone is randomly distributed over the polyester.
 4. The composition of claim 1 wherein the polyester has an average M/E ratio of at least
 20. 5. The composition of claim 1 wherein the amount of polypropylene is from 5-95 wt. % on the basis of the total amount of polyethylene and polypropylene.
 6. The composition of claim 1 wherein the amount of compatibiliser is from 0.5-10 wt. % on the basis of the sum of the amount of polypropylene and polyethylene.
 7. The composition of any claim 1 wherein said polypropylene is one or more of: a propylene homopolymer, a propylene—α-olefin random copolymer, a propylene—α-olefin block copolymer, a heterophasic polypropylene copolymer comprising a matrix phase and a disperse phase, the matrix phase consisting of a propylene homopolymer and/or a propylene copolymer with up to 3 wt. % of ethylene and/or at least one C₄-C₈ α-olefin, the wt. % being based on the matrix phase, and the disperse phase consisting of an ethylene—C₃-C₈ α-olefin copolymer.
 8. The composition of claim 1 wherein said polyethylene is a very low density polyethylene, linear low density polyethylene, low density polyethylene, high density polyethylene or a mixture of any of the foregoing polyethylenes.
 9. The composition of claim 1 wherein the compatibiliser has a number average molecular weight of from 5000 to 250000 g/mol.
 10. The composition of claim 1 wherein in the compatibiliser the polyester is selected from one or more selected from the group consisting of polytetradecalactone, polypentadecalactone, polyhexadecalactone, poly(caprolactone-co-pentadecalactone), poly(ε-decalactone-co-pentadecalactone), poly(ethylene brassylate-co-pentadecalactone), poly[ethylene-1,19-nonadecanedioate], poly[ethylene-1,23-tricosanedioate], poly[propylene-1,19-nonadecanedioate], poly[propylene-1,23-tricosanedioate], poly[1,4-butadiyl-1,19-nonadecanedioate], poly[1,4-butadiyl-1,23-tricosanedioate], poly[1,6-hexadiyl-1,19-nonadecanedioate], poly[1,6-hexadiyl-1,23-tricosanedioate], poly[1,19-nonadecadiyl-1,19-nonadecanedioate], poly[1,19-nonadecadiyl-1,23-tricosanedioate], poly[1,23-tricosadiyl-1,19-nonadecanedioate], poly[1,23-tricosadiyl-1,23-tricosanedioate], poly[1,20-icosadiyl-1,20-icosa-nedioate], poly[1,6-hexadiyl-1,20-icosenedionate], poly[propylene-1,20-icosanedionate].
 11. The composition of claim 1 wherein the polypropylene block of the compatibiliser is a propylene homopolymer block or a propylene copolymer block containing at least 90 wt. % of polypropylene, on the basis of the weight of the polypropylene block.
 12. An article comprising the composition of claim
 1. 13. The article of claim 12, said article being selected from the group consisting of automotive interior articles, automotive exterior articles, household appliances, pipes, films, sheets.
 14. The composition of any claim 7 wherein said polypropylene comprises a propylene ethylene or a propylene C₄-C₈ α-olefin random copolymer.
 15. A composition comprising polypropylene, polyethylene and a compatibiliser, wherein said compatibiliser is a block copolymer comprising a polypropylene block and a polyester block, said polyester being a non-aromatic polyester and having an average M/E ratio of at least 50, wherein M is the number of backbone carbon atoms in the polyester not including the carbonyl carbons and E is the number of ester groups in the polyester, and wherein the amount of polypropylene is from 5-95 wt. % and the amount of compatibiliser is from 5-10 wt. %, on the basis of the sum of the amount of polypropylene and polyethylene. 